1. Field of the Invention
The present invention relates to a liquid honing or liquid blasting apparatus using ice slurry (hereinafter referred to as surface processing apparatus using ice slurry) which performs such machining as fine processing or polishing of surface by blowing slurried ice grains onto the surface with high pressurized fluid. More specifically, it relates to a surface processing apparatus in which the ice slurry is introduced to a surface processing section and the slurry is spouted to a workpiece by the medium of an injection means in the surface processing section to perform the honing or blasting.
2. Description of the Related Art
Liquid blast or liquid honing (hereinafter both of these are referred to as liquid honing) of blowing onto the surface of a workpiece a suspension in which abrasive grains or granular substances are suspended, accelerating the suspension to high velocity by utilizing fluid pressure, is well known in the art. The honing is used extensively for removing burrs after machining, removing burrs of molded parts, fine processing, surface polishing, etc., using as injected substances polishing abrasive grains, glass beads, vegetable particles, and synthetic resin particles.
However, by the prior art mentioned above, the injected substance may remain on the surface of the workpiece, and changes in dimensions and damage to the processed surface may occur. For this reason, a large amount of cost and time are spent in the after-treatment, particularly in removing residue.
Several ice-blasting processes in which ice grains or dry ice grains are injected with a high pressure gas, are disclosed.
For example, there are disclosed an art of injecting only ice grains to the surface of a workpiece by utilizing an ejector in the Japanese Unexamined Patent Publication No. Sho 58-02674; an art of injecting frozen particles frozen in a low temperature atmosphere produced by the evaporated gas of a refrigerant, in the Japanese Patent Publication No. Hei 7-57471; and an art of ice-blast using dry ice grains, in the WO86/04536.
However, all of these arts are constituted so as to inject only ice grains or dry ice grains with a gas stream, and not accompanied with cleaning function. For this reason, there remain problems such as re-adhesion of scraped-off matter once scraped off the workpiece; accumulation and agglomeration of ice on the surface of the workpiece; and pipe blockage with the ice or dry ice grains, the substances to be injected, in the process of the transfer to the injection portion, due to which the stable operation of the injection nozzle is not ensured.
An art of liquid honing (blast) using ice slurry to solve the problems mentioned above, is disclosed in the Japanese Unexamined Patent Publication No. Hei 8-309660.
According to the disclosure, although ice is used as substance to be injected for the sake of not causing damage on the processed surface of the workpiece the same as is used in the prior art of ice-blast, the ice is mixed with water to make ice slurry. The liquid honing is performed using the ice slurry in order to exclude the necessity of cleaning after the honing.
This prior art is shown in FIG. 6. As shown in the figure, lumps of ice 50 are crushed to ice grains in an ice grain manufacturing device 57, water 52 is cooled in a liquid storage tank 53, the ice grains formed in the ice grain manufacturing device 57 and the water cooled in the liquid storage tank 53 are supplied to the stirring mixer tank 55 to obtain an ice slurry 51 by stirring and mixing. The ice slurry 51 is supplied to a high pressure injection nozzle 22 through a pump 54, and injected therefrom with high pressure gas introduced from high pressure gas introducing pipe 58, to perform blast.
Thus, in this prior art, proper amount of ice grains of proper grain size are prepared in the ice grain manufacturing device 57 by crushing the lumps of ice 50 supplied by an ice lump supplying device not shown in the drawing; cooled water 52 of proper temperature is prepared in the liquid storage tank 53 by cooling the water supplied from a new water supplying part 17 by a unit cooler 56; the prepared ice grains and cooled water 52 are supplied by proper amount to the stirring mixer tank 55 from the ice grains manufacturing device 57 and the liquid storage tank 53 respectively; thereby an ice slurry of proper concentration is formed by stirring and mixing; and the ice slurry is transferred by the medium of the pump 54 to the high pressure injection nozzle 22 to be injected therefrom to perform surface processing.
Injection discharge water 28 collected to a discharge liquid collecting tank 20a provided in the liquid honing section 21, is returned to the liquid storage tank 53 through a drain pump 22b and a filter 22c. The liquid storage tank 53 is also replenished with new water supplied from the new water supplying part 17 to keep a predetermined level.
However, there remain also in this prior art the following problems: an ice grain manufacturing section for crushing lumps of ice so as to reduce them to ice grains of proper grain size is needed along with an ice lump feeder, which results in the high cost of equipment; it is difficult to obtain ice grains of uniform diameter in the ice grain manufacturing section in which ice lumps are crushed mechanically, and with nonuniform grain size the blast performance is unstable; a stirring mixer tank is needed to obtain ice grains of proper concentration by mixing the crushed ice grains with the water cooled by a cooling unit; and even with the mixer tank, the concentration of the ice slurry is apt to be unstable, as the ice grains and the water cooled by the chiller are supplied separately to be mixed.